sched/wait, fs/btrfs: Convert wait_on_atomic_t() usage to the new wait_var_event() API

The old wait_on_atomic_t() is going to get removed, use the more
flexible wait_var_event() API instead.

No change in functionality.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: David Sterba <dsterba@suse.com>
Cc: Chris Mason <clm@fb.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

fs/btrfs/extent-tree.c

@@ -3990,7 +3990,7 @@ void btrfs_dec_nocow_writers(struct btrfs_fs_info *fs_info, u64 bytenr)
 	bg = btrfs_lookup_block_group(fs_info, bytenr);
 	ASSERT(bg);
 	if (atomic_dec_and_test(&bg->nocow_writers))
-		wake_up_atomic_t(&bg->nocow_writers);
+		wake_up_var(&bg->nocow_writers);
 	/*
 	 * Once for our lookup and once for the lookup done by a previous call
 	 * to btrfs_inc_nocow_writers()
@@ -4001,8 +4001,7 @@ void btrfs_dec_nocow_writers(struct btrfs_fs_info *fs_info, u64 bytenr)
 
 void btrfs_wait_nocow_writers(struct btrfs_block_group_cache *bg)
 {
-	wait_on_atomic_t(&bg->nocow_writers, atomic_t_wait,
-			 TASK_UNINTERRUPTIBLE);
+	wait_var_event(&bg->nocow_writers, !atomic_read(&bg->nocow_writers));
 }
 
 static const char *alloc_name(u64 flags)
@@ -6526,7 +6525,7 @@ void btrfs_dec_block_group_reservations(struct btrfs_fs_info *fs_info,
 	bg = btrfs_lookup_block_group(fs_info, start);
 	ASSERT(bg);
 	if (atomic_dec_and_test(&bg->reservations))
-		wake_up_atomic_t(&bg->reservations);
+		wake_up_var(&bg->reservations);
 	btrfs_put_block_group(bg);
 }
 
@@ -6552,8 +6551,7 @@ void btrfs_wait_block_group_reservations(struct btrfs_block_group_cache *bg)
 	down_write(&space_info->groups_sem);
 	up_write(&space_info->groups_sem);
 
-	wait_on_atomic_t(&bg->reservations, atomic_t_wait,
-			 TASK_UNINTERRUPTIBLE);
+	wait_var_event(&bg->reservations, !atomic_read(&bg->reservations));
 }
 
 /**
@@ -11061,7 +11059,7 @@ void btrfs_wait_for_snapshot_creation(struct btrfs_root *root)
 		ret = btrfs_start_write_no_snapshotting(root);
 		if (ret)
 			break;
-		wait_on_atomic_t(&root->will_be_snapshotted, atomic_t_wait,
-				 TASK_UNINTERRUPTIBLE);
+		wait_var_event(&root->will_be_snapshotted,
+			       !atomic_read(&root->will_be_snapshotted));
 	}
 }

fs/btrfs/ioctl.c

@@ -723,7 +723,7 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
 	btrfs_subvolume_release_metadata(fs_info, &pending_snapshot->block_rsv);
 dec_and_free:
 	if (atomic_dec_and_test(&root->will_be_snapshotted))
-		wake_up_atomic_t(&root->will_be_snapshotted);
+		wake_up_var(&root->will_be_snapshotted);
 free_pending:
 	kfree(pending_snapshot->root_item);
 	btrfs_free_path(pending_snapshot->path);